Magnetic recorder/reproduction apparatus including a selective temperature controller and magnetic recording reproduction method including selective temperature control

ABSTRACT

A magnetic recording-reproduction apparatus in accordance with the present invention, which carries out recording and reproducing processes on and from a magnetic recording-reproducing medium on which a perpendicular magnetic recording layer made of a ferrimagnetic material whose magnetic compensation temperature is set to approximately room temperature is formed, is arranged so that the length direction of the main magnetic pole of the head is made coincident with the information track direction. The magnetic recording-reproduction apparatus is also provided with a recording-reproducing magnetic head constituted by at least two single magnetic pole heads that are aligned side by side, and a means for raising the temperature of one portion of the magnetic recording-reproducing medium facing the main magnetic pole of each single magnetic pole head. With this arrangement, it becomes possible to avoid crosstalk over a plurality of tracks, and since it is possible to eliminate the need for a magnetic head having recording and reproducing single magnetic pole heads in a hybrid manner, the head manufacturing process can be simplified.

FIELD OF THE INVENTION

The present invention relates to a magnetic recording-reproductionapparatus and a magnetic recording-reproduction method that arepreferably used in a perpendicular magnetic recording system of anoptical assist type, etc. and that are capable of performinghigh-density recording in a magnetic disk device and a magnetic tapedevice.

BACKGROUND OF THE INVENTION

Tremendous research efforts have been directed to a perpendicularmagnetic recording system for a long time as a system which can carryout recording with higher density as compared with a system that carriesout magnetic recording in the longitudinal direction (in the in-planedirection) (longitudinal magnetic recording system). In order to achievea next-generation magnetic recording technique that enables a recordingdensity exceeding 10 Gb/in², various studies and developing efforts havebeen directed to designs and machining processes for heads and mediahaving constructions that unitize features of the perpendicular magneticrecording system. In particular, with respect to magnetic heads used forperpendicular magnetic recording/reproducing processes, studies havebeen directed to a single magnetic pole head which has an optimalconstruction.

Along with the recent developments in the technique for achieving higherdensity in the longitudinal magnetic recording system, a method in whichthe thickness of the main magnetic pole of the single magnetic pole headis made equal to the track width has been proposed and this method hasattracted public attention as a recording system which well utilizes thehigh-density recording characteristic of the perpendicular magneticrecording (for example, see IEEE Transactions On Magnetics, vol. 30, No.6, November, 1994, pp3900-3902).

In this method, information is written by using a plurality of recordingsingle magnetic pole heads that are aligned in a direction parallel tothe track direction of a magnetic medium, and information is read out byusing a plurality of reproducing single magnetic pole heads that arealigned in a direction perpendicular to the track direction. This methodmakes it possible to carry out a deep sub-micron track recording with atrack width of not more than 0.5 μm.

Moreover, also in a tracking servo system and a high-speed accessingsystem for such high-density tracks, a track following technique withhigher precision which exceeds the conventional servo performances isrequired. For this reason, in a separate manner from the above-mentionedrecording single magnetic pole head, a reproducing single magnetic polehead is installed and its main magnetic pole is aligned so as to makethe length direction perpendicular to the tracks; thus, the head isdesigned so as to have a wider width in the track traversing directionso that a multi-track reproducing is carried out. Here, the tracking isperformed based upon the above-mentioned reproducing single magneticpole head so as to meet the high-speed reproducing process and trackfollowing process.

However, in the above-mentioned conventional apparatus, the reproducingprocess is carried out by using one single magnetic pole head in amanner so as to extend over a plurality of tracks; consequently, piecesof information on a plurality of tracks are simultaneously reproduced,with the result that crosstalk tends to occur. For this reason, anadvanced multivalued signal processing circuit, etc., which iscompletely different from that of the conventional magnetic recordingsignal process, is required in a separate manner. The resulting problemis that an extremely complex magnetic recording-reproduction apparatusis required.

Moreover, in the conventional apparatus having a reproducing singlemagnetic pole head in a separate manner from the recording singlemagnetic pole head, a magnetic head, which has two heads, that is, arecording single magnetic pole head and a recording single magnetic polehead, in a hybrid manner, has to be installed. The resulting problem isthat a complicated head manufacturing process is required.

DISCLOSURE OF THE INVENTION

In order to solve the above-mentioned problems, a magneticrecording-reproduction apparatus in accordance with the presentinvention, which carries out recording and reproducing processes on andfrom a magnetic recording-reproducing medium on which a perpendicularmagnetic recording layer made of a ferrimagnetic material whose magneticcompensation temperature is set to approximately room temperature isformed, is provided with: a recording-reproducing magnetic headconstituted by a plurality of single magnetic pole magnetic heads havingrespective main magnetic poles whose length directions are aligned inthe same direction as the information track direction of the magneticrecording-reproducing medium, the recording-reproducing magnetic headbeing used for both recording and reproducing; and a temperature-raisingmeans for allowing an area facing the main magnetic poles of therespective single magnetic pole heads in the perpendicular magnetizationlayer to have a temperature rise.

In the above-mentioned arrangement, the recording-reproducing magnetichead is constituted by not less than two of the single magnetic polemagnetic heads which have respective main magnetic poles whose lengthdirections are aligned in the same direction as the information trackdirection of the magnetic recording-reproducing medium, and which areused for both recording and reproducing. This makes it possible toincrease the tracking density. The magnetic recording-reproducing mediumused in the above-mentioned magnetic recording-reproduction apparatus isprovided with the perpendicular magnetic recording layer made from aferrimagnetic material having a magnetic compensation temperature set toapproximately room temperature; therefore, an area (portion) of therecording layer that is virtually at room temperature exhibits a smallersaturated magnetization, thereby minimizing the leakage magnetic fluxtherefrom.

The following description will discuss a process in which information isrecorded and reproduced on and from the above-mentioned magneticrecording-reproduction medium by using the recording-reproducingmagnetic head. In this case, one portion of an area in the perpendicularmagnetic recording layer facing the main magnetic poles of the singlemagnetic pole heads is subjected to a temperature rise (for example, byirradiation with a light beam or heating by using a minute thermalsource), and the recording and reproducing processes are carried out asfollows:

When, upon recording, the temperature of a recording area is raised tothe vicinity of the Curie temperature so that the coercive force of theperpendicular magnetic recording layer becomes nearly zero, the leakagemagnetic field from the single magnetic pole heads is applied to therecording area so that the information is readily recorded thereon. Inother words, a high track density is achieved by a recording processusing the narrow track that nearly corresponds to the width of each mainmagnetic pole of the single magnetic pole heads.

In contrast, when, upon reproducing, the temperature of a reproducingarea is raised so as to allow the saturated magnetization of theferrimagnetic material to reach the vicinity of the maximum value, anon-temperature-rise area, that is, an area that faces the main magneticpoles of the single magnetic pole heads and is maintained in thevicinity of the magnetic compensation temperature (virtually, roomtemperature); therefore, a magnetic flux released from the saturatedmagnetization only from the temperature-rise area (reproducing area) isdetected by the single magnetic pole heads facing the area with highprecision. This makes it possible to positively solve the conventionalproblem that information separation is not properly made due to theoperation carried out in a manner extending over a plurality ofrecording bits in the track direction, and consequently to reproduceinformation recorded with high linear density that is an originalfeature of the perpendicular magnetic recording system.

Moreover, it is not necessary to install separated sets of singlemagnetic pole heads respectively used for recording and reproducing, andthis eliminates the need for a special signal processing such as amulti-value processing that is required for a multi-track batchreproducing process in the case of a single reproducing head.Furthermore, in the case when an optical beam is used to raise thetemperatures of the recording area and the reproducing area, ahigh-precision tracking operation is available by using the optical beamapplied thereto.

Here, the gap between the single magnetic pole heads can be widened byorienting the alignment direction of the single magnetic pole heads withan angle with respect to the direction of the information tracks; thus,it is possible to reduce magnetic interferences from the adjacent singlemagnetic pole heads, and consequently to provide information recordingand reproducing processes with a further improved S/N ratio.

Moreover, the application of an arrangement in which an elliptical areaelongated in the aligning direction of the single magnetic pole heads isused as the temperature-rise area makes it possible to raise thetemperature of an area of the perpendicular magnetization recordinglayer facing the single magnetic pole heads at one time, andconsequently to simplify the temperature-raising means as well as tosuppress the expansion of the temperature distribution of thetemperature-rise area in the track direction. Thus, a bit recordingprocess, which is virtually determined by the shape of the main magneticpole of the single magnetic pole head, can be carried out with higherlinear density.

Furthermore, it becomes possible to make the magneticrecording-reproduction apparatus thinner by arranging therecording-reproducing magnetic head and the temperature raising means onthe same side as the perpendicular magnetic recording layer.

For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1(a) is a schematic drawing showing a magneticrecording/reproduction apparatus in accordance with Embodiment 1 of thepresent invention wherein the magnetic head and the temperature raisingmeans face each other on opposite sides of the magneticrecording/reproducing medium;

FIG. 1(b) is a schematic front view of a representative magneticrecording-reproducing medium used in Embodiment 1 of the presentinvention;

FIG. 2 is a schematic view similar to that of FIG. 1(b) showing arepresentative magnetic recording-reproducing medium used withEmbodiment 2 of the present invention in which the magnetic head and thetemperature raising means are set at an acute angle relative to thetracks on the recording-reproducing medium;

FIG. 3 is a schematic drawing showing a magnetic recording-reproductionapparatus in accordance with another embodiment of the present inventionwherein the magnetic head and the temperature raising means are disposedon the same side of the magnetic recording-reproducing medium;

FIG. 4 is a schematic drawing showing a magnetic recording-reproductionapparatus in accordance with yet another embodiment of the presentinvention similar to that shown in FIG. 3, but wherein a triangularprism is utilized to direct temperature raising input against therecording-reproducing medium;

FIG. 5 is a schematic drawing showing a magnetic recording-reproductionapparatus in accordance with yet another embodiment of the presentinvention similar to that shown in FIG. 3, but wherein a taper shapedwaveguide is utilized to direct temperature raising input against therecording-reproducing medium;

FIG. 6 is a schematic drawing showing a magnetic recording-reproductionapparatus in accordance with yet another embodiment of the presentinvention similar to that shown in FIG. 3, but wherein the temperatureraising means and magnetic head are disposed at substantially equalacute angles to opposite sides of a plane perpendicular to therecording-reproduction medium that meet substantially at the surface ofthe recording-reproducing medium; and,

FIG. 7 is a schematic drawing showing a magnetic recording-reproductionapparatus in accordance with yet another embodiment of the presentinvention similar to that shown in FIG. 1 indicating that thetemperature raising means of this invention may comprise a heatgenerating means located in close relation to the space between themagnetic head and the magnetic recording-reproducing medium.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to Figures, the following description will discuss the bestmode for carrying out the invention.

FIG. 1(a) is a schematic drawing that shows the entire construction of amagnetic recording-reproduction apparatus in accordance with Embodiment1 of the present invention.

Moreover, FIG. 1(b) is a front view that shows a magneticrecording-reproducing medium used in the present invention.

As illustrated in FIG. 1(a), the magnetic recording-reproductionapparatus of the present invention is provided with a light beamirradiation system 15 (temperature-raising means) mainly constituted bya laser light source 1 which is constituted by a semiconductor laser andwhich, upon recording as well as reproducing, generates (releases) alight beam so as to raise the temperature of a desired area on amagnetic recording-reproducing layer 7, a cylindrical lens 2 and anobjective lens 3. The present magnetic recording-reproduction apparatusis further provided with a recording-reproducing magnetic head 5 made bymulti-arranging at least two (four in the present embodiment) singlemagnetic pole heads 4 with the same intervals, that have main magneticpoles whose length directions (perpendicular direction in the Figure)are aligned in the track direction, and a magnetic disk 16 (magneticrecording-reproducing medium) made of a disk substrate 6 and aperpendicular magnetic recording layer 7.

The above-mentioned recording-reproducing magnetic head 5 has aplurality of single magnetic pole heads 4 that are aligned with the sameintervals, and each single magnetic pole head 4 has both functions as arecording magnetic head and as a reproducing magnetic head so that evenonly the recording-reproducing head 5 can carry out recording andreproducing processes when a recording area and a reproducing area areallowed to have temperature rises.

In the above-mentioned magnetic disk 16, guiding grooves 9 and lands 10are formed on its surface in the shape of concentric circles or in aspiral form.

As illustrated in FIG. 1(b), in the light beam irradiation system 15,the cylindrical lens 2 is placed between the laser light beam 1 and theobjective lens 3 so as to shape the light beam 8 into an elliptical beam(an elliptical shape). With this arrangement, it is possible tosimultaneously irradiate a plurality of information tracks 13 within theelliptical beam with its major axis being coincident with the alignmentdirection of the single magnetic pole heads 4 that are arrangedlaterally with respect to the information tracks (arranged in adirection perpendicular to the track direction with predeterminedintervals). Here, although not shown in the Figure, an optical systemfor focusing servo and tracking servo operations may be installed in theoptical beam irradiation system 15 on demand.

The magnetic disk 16 is constituted by a perpendicular magneticrecording layer 7 made of a ferrimagnetic material having its magneticcompensation point temperature (hereinafter, referred to as compensationtemperature) at virtually room temperature and a disk substrate 6.

With respect to the ferrimagnetic material, taking into considerationthe permissible power of the semiconductor laser for the laser lightsource 1 used for giving a temperature rise at the time of recording orreproducing, it is preferable to set the temperature for allowing thesaturated magnetization of the ferrimagnetic material to have a maximumvalue at the time of reproducing in the range of 120° C. to 240° C., andwith respect to the Curie temperature that gives influences to therecording sensitivity, it is preferably to set it in the range of 200°C. to 350° C. Moreover, in order to obtain a sufficient reproducingoutput from each single magnetic pole head 4 at the time of reproducing,taking into consideration the reproducing sensitivity of the singlemagnetic pole head 4, it is preferable to select a material having asaturated magnetization of at least 150 emu/cc as the ferrimagneticmaterial. With respect to materials satisfying the above-mentionedrequirements, for example, Dy_(x)(Fe_(1−y)Co_(y))_(1−x) andTb_(x)(Fe_(1−y)Co_(y))_(1−x), etc. are listed. In these cases, x and yare respectively set so as to satisfy 10<×<40 and 10 <y <50.

With respect to the disk substrate 6, materials having alight-transmitting property, such as glass, glass ceramics, sapphire,polycarbonate and amorphous polyolefin, are used.

Here, in the case of a magnetic recording-reproduction apparatus of thetype in which, with respect to the magnetic disk 16, the light beamirradiation system 15 and the recording-reproducing magnetic head 5 areplaced on the same side as the perpendicular magnetization recordinglayer 7 formation side (see FIG. 3), a material having alight-transmitting property is not necessarily required as the disksubstrate material; and for example, an Al substrate with an NiPunderlayer, opaque ceramics, etc., may be used.

Guide grooves 9 and lands 10 are alternately formed on the surface ofthe disk substrate 6. In the present embodiment, four information tracks13 are formed for each land 10. A row of information bits 12 arerecorded on each information track 13 through the corresponding singlemagnetic pole head 4, and information bits 12, recorded through thecorresponding single magnetic pole head 4, are read from the informationtrack 13 (see FIG. 1(b)). In this case, since the light beam 8 isallowed to shift together with the recording-reproducing magnetic head 5along the guide groove 9, the track-following operation is carried out.

Next, referring to FIG. 1(b), an explanation will be given of aninformation recording process which is carried out by using the magneticrecording apparatus of the present invention. First, a driving electriccurrent, which varies in accordance with recorded information, isallowed to flow from a driving circuit (not shown) through a coil (notshown) that is wound around each single magnetic pole head 4 so that thesingle magnetic pole head 4 is magnetically excited, while a light beam8 is directed onto the surface of the recording-reproducing medium 14 sothat one portion thereof (a desired recording portion) facing the mainpole of the single magnetic pole head 4 is subjected to a temperaturerise up to the vicinity of the Curie temperature of the ferrimagneticmaterial.

Since the above-mentioned perpendicular magnetic recording layer 7 ismade of a ferrimagnetic material having its compensation temperature atvirtually room temperature, only the portion irradiated with the lightbeam 8 (temperature rise portion) in the perpendicular magneticrecording layer 7 is heated up to the vicinity of the Curie temperature,and this portion comes to have a smaller coercive force. When a magneticfield generated by the magnetized main pole of the single magnetic polehead 4 is applied to the area having a smaller coercive force, amagnetization reversal occurs only at the corresponding area, with theresult that an information bit 11 is recorded as illustrated in FIG.1(b). At this time, since the magnetic field distribution is limited toapproximately the thickness of the main pole of the single magnetic polehead 4, the width of the information track 13 is also limited to notmore than 0.5 μm, thereby making it possible to perform a hightrack-density recording process, that is, a so-called deep sub-microntrack recording process.

Moreover, the application of the light beam 8 (see FIG. 1(b)) having anelliptical shape elongated in the aligning direction of the singlemagnetic pole heads 4 makes it possible to suppress the expansion of thetemperature distribution in the information track direction, that is,the expansion of the distribution of the coercive force; therefore, arectangular-shaped bit recording process, which is virtually determinedby the shape of the main magnetic pole of the single magnetic pole head4, can be carried out with high recording density also in the trackdirection.

As described in the present embodiment, in an attempt to simplify theapparatus and to uniform the irradiated portion, it is preferably toadopt the irradiated portion by the light beam that is formed into anelliptical shape; however, the present invention is not intended to belimited by this arrangement, and another arrangement may be used inwhich each information bit 11 to be recorded or reproduced isindividually irradiated with light.

Next, also referring to FIG. 1(b), an explanation will be given of aninformation reproducing process which is carried out by using themagnetic recording apparatus of the present invention.

A light beam 8 is directed to one portion (desired reproducing portion)of the surface of the recording-reproducing medium 14 facing the mainpole of the single magnetic pole head 4 so that it is subjected to atemperature rise to the vicinity of a temperature (120° C. to 240° C.)that allows the saturated magnetization of the perpendicular magneticrecording-reproducing medium (perpendicular magnetic recording layer 7)to have a maximum value.

In the perpendicular magnetic recording layer 7, only the magnetizationbecomes greater at the reproducing area having the temperature rise sothat a leakage magnetic flux from the reproducing area (reproducingportion) is detected by the single magnetic pole head 4; thus, it ispossible to read the information bit 11 as information.

At this time, in the above-mentioned perpendicular magnetic recordinglayer 7, an area (non-irradiated portion) that has not been subjected tothe irradiation by the light beam 8 does not have a temperature rise,and is maintained at a magnetic compensation temperature that is set tovirtually room temperature; therefore, since the saturated magnetizationis small and since magnetic flux leakage therefrom is also small, noinformation is simultaneously read from the non-irradiated portion. Inother words, of an area on the information tracks 13 of the magneticrecording-reproducing medium facing the main poles of the singlemagnetic pole heads 4, only the area (portion) irradiated with the lightbeam 8 is allowed to reproduce the information bit 11.

For this reason, even if the length direction of the main poles of thesingle magnetic pole heads 4 is made coincident with the trackdirection, it is possible to avoid simultaneously reading informationbits 11 recorded in the track direction with high density in a bridgingmanner together with a plurality of bits located before and after, andconsequently to reproduce information recorded with high linear densitythat is an original feature of the perpendicular magnetic recordingsystem. Moreover, in the same manner as the recording process, thetrack-following operation is carried out with high precision also in thereproducing process by utilizing the light beam 8 having the ellipticalshape.

Moreover, even in the case when the single magnetic pole head 4 has atracking deviation, since the influence appears in the reproduced signalfrom the single magnetic pole head 4 in the same manner, it is possibleto easily compensate for the deviation. As described above, in themagnetic recording-reproduction apparatus of the present invention, boththe recording and reproducing processes of information can be carriedout by using the same recording-reproducing magnetic head 5 and theoptical beam irradiation system 15.

In the present embodiment, in order to form the light beam 8 having anelliptical shape, the cylindrical lend 2 is used; however, the presentinvention is not intended to be limited by this arrangement, and inplace of the cylindrical lens 2, for example, another arrangement may beadopted in which a laser beam, released from a semiconductor laser ofthe laser light source 1 is formed into an elliptical shape with apredetermined ratio of the major and minor axes by utilizing atriangular prism (see, FIG. 4), etc., or in which the shape is changedwhile being allowed to pass through a waveguide having a taper shape(see, FIG. 5).

Moreover, in the present embodiment, the explanation has been given ofthe case in which the recording- reproducing magnetic head 5 and thelight beam irradiation system 15 are aligned face to face, with themagnetic disk 16 being interpolated in between; however, the presentinvention is not intended to be limited to this arrangement, and both ofthe parts may be placed on the same side as the formation side of theperpendicular magnetic recording layer 7 with respect to the magneticdisk 16 (see, FIG. 3). This arrangement easily makes the apparatusthinner. In this case, Since the perpendicular magnetic recording layer7 needs to be heated prior to the recording or reproducing process bythe recording-reproducing magnetic head 5, the light beam irradiationsystem 15 is placed on the leading edge side of the main magnetic polesof the single magnetic pole heads 4 in the proximity of therecording-reproducing magnetic head 5 so that an area of theperpendicular magnetic recording layer 7 facing the leading edge issubjected to a temperature rise.

In the present embodiment, the magnetic disk 16 is used as therecording-reproducing medium; however, the present invention is notintended to be limited by this, and other media such as magnetic tapesmay be used.

Moreover, in the above-mentioned embodiment, the light beam irradiationsystem 15 is exemplified as the temperature-raising means; however, thepresent invention is not intended to be limited by this. With respect tothe temperature raising means, a minute heat source system, made of aminute heat generating body placed in the proximity of the recordingsection and the reproducing section, may be adopted as the temperatureraising means (see, for example, FIG. 7). In this case, the heatapplying width of the minute heat generating body in the traversingdirection of the information tracks is set in a manner so as to bridge aplurality of information tracks. With respect to the minute heatgenerating body, metal materials, such as tungsten, tantalum, molybdenm,nickel-chromium alloy, iron-chromium-aluminum alloy, having a superiorheat generating efficiency, and non-metal materials, such as siliconcarbide, boron nitride and ruthenium oxide, may be adopted.

Next, with respect to the second embodiment of the present invention, anexplanation will be given of a case in which the single magnetic poleheads 4 are placed with an angle with respect to the direction of theinformation tracks 13 (information track direction). FIG. 2 shows a topview of a magnetic recording-reproducing medium in accordance with thepresent embodiment (see also FIG. 6). Here, those members that have thesame functions as those shown in FIG. 1 are Indicated by the samereference numerals, and the detailed description thereof is omitted.

The present embodiment is different from the first embodiment in thefollowing points as will be recognized, for example, in conjunction withFIGS. 2 and 6. In the present embodiment, in the recording-reproducingmagnetic head 5 the respective single magnetic pole heads 4 are arrangedso that, as illustrated in FIG. 2, information bits 11 are diagonallyformed with an angle θ with respect to the information tracks 13. Inthis case also, the single magnetic ole heads 4 are respectively placedwith predetermined distances in the direction of the information tracks.In accordance with the arrangement of the respective magnetic pole heads4, the light beam 8, directed from the laser light source 1 at the timeof recording as well as reproducing, is directed onto the perpendicularlayer 7 in an elliptical shape having a tilt by the angle θ in the majoraxis direction with respect to the track direction.

Next, referring to FIG. 2, an explanation will be given of aninformation recording process which is carried out by using the magneticrecording apparatus of the present embodiment. First, a driving electriccurrent, which varies in accordance with recorded information, isallowed to flow from a driving circuit (not shown) through a coil (notshown) that is wound around each single magnetic pole head 4 so that thesingle magnetic pole head 4 is magnetically excited, while a light beam8 is directed in an elliptical shape having a tilt by the angle of θ inthe major axis direction with respect to the track direction. As aresult, a recording portion on the surface of the recording-reproducingmedium 14 facing the main poles of the single magnetic pole heads 4 issubjected to a temperature rise up to the vicinity of the Curietemperature of the ferrimagnetic material.

Since the above-mentioned perpendicular magnetic recording layer 7 ismade of a ferrimagnetic material having its compensation temperature atvirtually room temperature, only the portion irradiated with the lightbeam 8 (temperature rise portion) in the perpendicular magneticrecording layer 7 is heated up to the vicinity of the Curie temperature,and this portion comes to have a smaller coercive force. When a magneticfield generated by the magnetized main pole of the single magnetic polehead 4 is applied to the area having a smaller coercive force, a fluxreversal occurs only at the corresponding area, with the result that aninformation bit 11 is recorded diagonally with the angle θ with respectto the information tracks 13 as illustrated in FIG. 2. At this time,since the magnetic field distribution is limited to approximately thethickness of the main pole of the single magnetic pole head 4, the widthof the information track 13 is also limited to not more than 0.5 μm,thereby making it possible to perform a high track-density recordingprocess, that is, a so-called deep sub-micron track recording process.

Moreover, the application of the light beam 8 having an elliptical shapeelongated in the aligning direction of the single magnetic pole heads 4makes it possible to suppress the expansion of the temperaturedistribution in the information track direction, that is, the expansionof the distribution of the coercive force; therefore, arectangular-shaped bit recording process, which is virtually determinedby the shape of the main magnetic pole of the single magnetic pole head4, can be carried out with high recording density also in the trackdirection.

As described in the present embodiment, in an attempt to simplify theapparatus and to uniform the irradiated portion, it is preferable toarrange so that the irradiated portion by the light beam is formed intoan elliptical shape having a tilt by the angle of θ in the major axisdirection with respect to the track direction (see, FIG. 6); however,the present invention is not intended to be limited by this arrangement,and another arrangement may be used in which each information bit 11 tobe recorded or reproduced is individually irradiated with light.

Next, also referring to FIG. 2, an explanation will be given of aninformation reproducing process which is carried out by using themagnetic recording apparatus of the present embodiment.

A light beam 8, formed into an elliptical shape having a tilt by theangle of θ in the major axis direction with respect to the trackdirection, is directed to a desired reproducing portion (correspondingto an information bit 11 in FIG. 2) of the surface of therecording-reproducing medium 14 facing the main pole of the singlemagnetic pole head 4 so that it is subjected to a temperature rise tothe vicinity of a temperature (120° C. to 240° C.) that allows itssaturated magnetization to have a maximum value.

In the perpendicular magnetic recording layer 7, only the magnetizationbecomes greater at the reproducing area having the temperature rise sothat a leakage magnetic flux from the reproducing portion is detected bythe single magnetic pole head 4; thus, it is possible to read theinformation bit 11 as information.

At this time, in the above-mentioned perpendicular magnetic recordinglayer 7, an area (non-irradiated portion) that has not been subjected tothe irradiation by the light beam 8 does not have a temperature rise,and is maintained at a magnetic compensation temperature that is set tovirtually room temperature; therefore, since the saturated magnetizationis small and since magnetic flux leakage therefrom is also small, noinformation is simultaneously read from the non-irradiated portion. Inother words, of an area on the information tracks 13 of the magneticrecording-reproducing medium facing the main poles of the singlemagnetic pole heads 4, only the area (portion) irradiated with the lightbeam 8 is allowed to reproduce the information bit 11.

For this reason, even if the length direction of the main poles of thesingle magnetic pole heads 4 is made coincident with the trackdirection, it is possible to avoid simultaneously reading informationbits 11 recorded in the track direction with high density in a bridgingmanner together with a plurality of bits located before and after, andconsequently to reproduce information recorded with high linear densitythat is an original feature of the perpendicular magnetic recordingsystem. Moreover, in the same manner as the recording process, thetrack-following operation is carried out with high precision also in thereproducing process by utilizing the light beam 8 having the ellipticalshape.

Moreover, even in the case when the single magnetic pole head 4 has atracking deviation, since the influence appears in the reproduced signalfrom the single magnetic pole head 4 in the same manner, it is possibleto easily compensate for the deviation. As described above, in themagnetic recording-reproduction apparatus of the present invention, boththe recording and reproducing processes of information can be carriedout by using the same recording-reproducing magnetic head 5 and theoptical beam irradiation system 15.

In the present embodiment, in order to form the light beam 8 having anelliptical shape, the cylindrical lens 2 is used; however, the presentinvention is not intended to be limited by this arrangement, and inplace of the cylindrical lens 2, for example, another arrangement may beadopted in which the laser beam, released from a semiconductor laser ofthe laser light source 1 is formed into an elliptical shape with apredetermined ratio of the major and minor axes by using a triangularprism (see FIG. 4), etc., or in which the shape is changed while beingallowed to pass through a waveguide having a taper shape (see FIG. 5).

Moreover, in the present embodiment, the explanation has been given ofthe case in which the recording-reproducing magnetic head 5 and thelight beam irradiation system 15 are aligned face to face, with themagnetic disk 16 being interpolated in between; however, the presentinvention is not intended to be limited to this arrangement, and bothparts may be placed on the same side as the formation side of theperpendicular magnetic recording layer 7 with respect to the magneticdisk 16 (see, FIG. 3). This arrangement easily makes the apparatusthinner. In this case, since the perpendicular magnetic recording layer7 needs To be heated prior to the recording or the reproducing processby the Recording-reproducing magnetic head 5, the light beam irradiationsystem 15 is placed on the leading edge side of the main magnetic polesof the single magnetic pole heads 4 in the proximity of therecording-reproducing magnetic head 5 so that an area of theperpendicular magnetic recording layer 7 facing the leading edge issubject to a temperature rise.

In the present embodiment, the magnetic disk 16 is used as the magneticrecording-reproducing medium; however, the present invention is notintended to be limited by this, and other media such as magnetic tapesmay be used.

Moreover, in the above-mentioned embodiment, the light beam irradiationsystem 15 is exemplified as the temperature raising means; however, thepresent invention is not intended to be limited by this. With respect tothe temperature-raising means, a minute heat source system, made of aminute heat generating body placed in the proximity of the recordingsection and the reproducing section, may be adopted (see, FIG. 7). Inthis case, the heat applying width of the minute heat generating body Inthe traversing direction of the information tracks is set in a manner soas to bridge a plurality of information tracks. With respect to theminute heat generating body, metal materials, such as tungsten,tantalum, molybdenum, nickel-chromium alloy, iron-chromium-aluminumalloy, having superior heat generating efficiency, and non-metalmaterials, such as silicon carbide, boron nitride and ruthenium oxide,may be adopted.

In the case of the application of the minute heat source system, it ispossible to carry out a tracking operation by using virtually the samemethod as the normal magnetic recording process. In other words, thetracking operation is carried out by recording a tracking servo signalas a magnetic signal. In this case, a pattern (servo pattern) that iscompletely different from the user data signal is preliminarily recordedalong the track intermittently, and this signal is read out through themagnetic head in the same manner as the user data. In the presentinvention, since the multi-head system is adopted, the servo pattern maybe provided for each track, or a physically large-size servo pattern maybe preliminarily recorded in a manner so as to bridge a plurality oftracks so that the servo signal is taken out based upon an operation(for example, a simple added signal) of reproduced signals from therespective magnetic heads.

In the same manner as the first embodiment, the application of theconstruction of the second embodiment makes it possible to obtain hightrack density and high linear recording density. Moreover, as comparedwith the first embodiment, since the distance between the informationbits 11 on adjacent tracks is widened, magnetic interference exerted onthe information bits 11 at the time of recording or reproducing issuppressed so that it is possible to record and reproduce informationwith a superior S/N ratio.

In the case when the magnetic recording and reproducing processes inaccordance with the second embodiment are carried out, it is preferableto set the ratio of the bit length (length represented by a in FIG. 2)in parallel with (track direction) the information track 13 which facesthe bottom face of the main magnetic pole of the single magnetic polehead 4 to the length between the tracks (length represented by b in FIG.2) in a direction perpendicular to the track direction to not morethan 1. For this reason, in order to widen the distance between thesingle magnetic pole heads 4 so as to effectively suppress theabove-mentioned magnetic interference, it is preferable to set tan θ tonot more than 1, that is, to set the angle θ to not more than 45degrees.

As described above, the magnetic recording-reproduction apparatus of thepresent invention, which carries out recording and reproducing processeson and from a magnetic recording-reproducing medium on which aperpendicular magnetic recording layer made of a ferrimagnetic materialwhose magnetic compensation temperature is set to approximately roomtemperature is formed, is provided with: a recording-reproducingmagnetic head constituted by not less than two single magnetic polemagnetic heads having respective main magnetic poles whose lengthdirections are aligned in the same direction as the information trackdirection of the magnetic recording-reproducing medium; and atemperature-raising means for allowing an area facing the main magneticpoles of the respective single magnetic pole heads in the perpendicularmagnetization layer to have a temperature rise.

With the above-mentioned arrangement, not less than two of the singlemagnetic pole magnetic heads which have respective main magnetic poleswhose length directions are aligned in the same direction as theinformation track direction of the magnetic recording-reproducingmedium, and a portion of an area of the perpendicular magnetic recordinglayer having the recording layer made from a ferrimagnetic materialhaving a magnetic compensation temperature set to approximately roomtemperature, which faces the main magnetic pole of the single magneticpole heads, is subjected to a temperature rise, for example, byirradiation with a light beam or heating by using a minute thermalsource, and the recording and reproducing processes are carried out asfollows:

When, upon recording, the temperature of a recording area is raised tothe vicinity of the Curie temperature so that the coercive force of theperpendicular magnetic recording layer becomes virtually zero, theleakage magnetic field from the single magnetic pole heads is applied tothe recording area so that the information is readily recorded thereon.In other words, a high track density is achieved by a recording processusing the narrow track that virtually corresponds to the width of eachmain magnetic pole of the single magnetic pole heads.

In contrast, when, upon reproducing, the temperature of a reproducingarea is raised so as to allow the saturated magnetization of theferrimagnetic material to reach the vicinity of the maximum value, anon-temperature-rise area, that is, an area that faces the main magneticpoles of the single magnetic pole heads and is maintained in thevicinity of the magnetic compensation temperature; therefore, a magneticflux released from the saturated magnetization only from thetemperature-rise area is detected by the single magnetic pole headsfacing the area with high precision. This makes it possible topositively solve the conventional problem that information separation isnot properly made due to the operation carried out in a manner bridgingover a plurality of recording bits in the track direction, andconsequently to reproduce information recorded with high linear densitythat is an original feature of the perpendicular magnetic recordingsystem.

Moreover, it is not necessary to install separated sets of singlemagnetic pole heads respectively used for recording and reproducing, andthis eliminates the need for a special signal processing such as amulti-value processing that is required for a multi-track reproducingprocess in the case of a single reproducing head. Furthermore, in thecase when an optical beam is used to raise the temperatures of therecording area and the reproducing area, a high-precision trackingoperation is available by using the optical beam applied thereto.

Here, the gap between the single magnetic pole heads can be widened byorienting the alignment direction of the single magnetic pole heads withan angle with respect to the direction of the information tracks; thus,it is possible to reduce magnetic interferences from the adjacent singlemagnetic pole heads, and consequently to provide information recordingand reproducing processes with a further improved S/N ratio.

Moreover, the application of an arrangement in which an elliptical areaelongated in the aligning direction of the single magnetic pole heads isused as the temperature-rise area makes it possible to raise thetemperature of areas of the perpendicular magnetic recording layerfacing the single magnetic pole heads at one time, and consequently tosimplify the temperature-raising means as well as to suppress theexpansion of the temperature distribution of the temperature-rise areain the track direction. Thus, a bit recording process, which isvirtually determined by the shape of the main magnetic pole of thesingle magnetic pole head, can be carried out with higher lineardensity.

Furthermore, it becomes possible to make the magneticrecording-reproduction apparatus thinner by arranging therecording-reproducing magnetic head and the temperature raising means onthe same side as the perpendicular magnetic layer (see FIGS. 3-6).

Industrial Applicability

As described above, the magnetic recording-reproduction apparatus andthe recording-reproduction method thereof in accordance with the presentinvention are preferably applied to the perpendicular magnetic recordingsystem which achieves high-density recording in apparatuses such asmagnetic disk apparatuses and magnetic tape apparatuses. In particular,with the arrangement in which the recording-reproducing magnetic head 5and the light beam irradiation system 15 (or a minute heat generatingbody) are placed on the same side as the perpendicular magneticrecording layer, the apparatus is preferably used for magneticrecording-reproduction apparatuses that particularly require thinness.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A magnetic recording-reproduction apparatus,which carries out recording and reproducing processes on and from anmagnetic-reproducing medium on which a perpendicular magnetic recordinglayer made of a ferrimagnetic magnetic material whose magneticcompensation temperature is set to approximately room temperature isformed, characterized by comprising: a recording-reproducing magnetichead constituted by a plurality of single magnetic pole magnetic headshaving respective main magnetic poles whose length directions arealigned in the same direction as the information track direction of themagnetic recording-reproducing medium, the recording-reproducingmagnetic head carrying out both recording and reproducing on and fromrespective different tracks; and temperature-raising means for allowingan area facing the main magnetic poles of the respective single magneticpole heads in the perpendicular magnetization layer to have atemperature rise.
 2. The magnetic recording-reproduction apparatusaccording to claim 1, characterized in that in the recording-reproducingmagnetic head, the single magnetic pole heads are arranged in adirection perpendicular to the information track direction withpredetermined intervals with the respective single magnetic pole headsbeing aligned to face the information tracks.
 3. The magneticrecording-reproduction apparatus according to claim 1, characterized inthat in the recording-reproducing magnetic head, the single magneticpole heads are arranged in a direction with a predetermined angle withrespect to the information track direction with the respective singlemagnetic pole heads being aligned to face the information tracks.
 4. Themagnetic recording-reproduction apparatus according to claim 1,characterized in that, upon recording, the temperature raising meansraises the temperature of a recording area to a temperature in thevicinity of the Curie temperature of the perpendicular magneticrecording layer, while, upon reproducing, the temperature raising meansraises the temperature of a reproducing area to a temperature thatallows the saturated magnetization of the perpendicular magneticrecording layer to reach the vicinity of a maximum value.
 5. Themagnetic recording-reproduction apparatus according to claim 4,characterized in that the temperature raising means raises thetemperature of the recording area or the reproducing area by applying alight beam thereto.
 6. The magnetic recording-reproduction apparatusaccording to claim 5, characterized in that the temperature raisingmeans comprises a light source for releasing the light beam and anoptical system for forming the light beam into a predetermined shape andfor converging the resulting light beam onto the recording area or thereproducing area.
 7. The magnetic recording-reproduction apparatusaccording to claim 6, characterized in that the optical system comprisesa cylindrical lens for forming the light beam into an elliptical shapeand an objective lens for converging light released from the cylindricallens onto the recording area or the reproducing area.
 8. The magneticrecording-reproduction apparatus according to claim 6, characterized inthat the optical system comprises a triangular prism for forming thelight beam into an elliptical shape and for directing the resultinglight beam to the recording area or the reproducing area.
 9. Themagnetic recording-reproduction apparatus according to claim 6,characterized in that the optical system comprises a taper-shapedwaveguide for changing the shape of the light beam.
 10. The magneticrecording-reproduction apparatus according to claim 4, characterized inthat the temperature raising means is a minute heat source system madeof a minute heat generating body for generating heat so as to raise thetemperature of the recording area or the reproducing area.
 11. Themagnetic recording-reproduction apparatus according to claim 1,characterized in that the recording-reproducing magnetic head and thetemperature raising means are placed on the same side of theperpendicular magnetic recording layer.
 12. The magneticrecording-reproduction apparatus according to claim 1, characterized inthat the recording-reproducing magnetic head and the temperature raisingmeans are placed on the opposite sides of the perpendicular magneticrecording layer.
 13. The magnetic recording-reproduction apparatusaccording to claim 1, characterized in that the temperature raisingmeans is placed close to one portion of the area facing the mainmagnetic poles of the respective single magnetic pole heads in themagnetic recording-reproducing medium.
 14. The magneticrecording-reproduction apparatus according to claim 10, characterized inthat the minute heat source system extends long in an alignmentdirection of the single magnetic pole heads.
 15. A magneticrecording-reproduction method, which carries out recording andreproducing processes on and from a magnetic recording medium on which aperpendicular magnetic recording layer made of a ferrimagmetic materialwhose magnetic compensation temperature is set to approximately roomtemperature is formed, by using a recording-reproducing magnetic headconstituted by a plurality of single pole magnetic heads havingrespective main magnetic poles whose length directions are aligned inthe same direction as the information track direction of the magneticrecording-reproducing medium, the recording-reproducing magnetic headcarrying out both recording and reproducing on and from respectivedifferent tracks, characterized by comprising the steps of: uponrecording, recording information through the recording-reproducingmagnetic head by raising the temperature of the recording area to thevicinity of the Curie temperature of the perpendicular magneticrecording layer; and upon reproducing, reading information from thereproducing area through the recording-reproducing head by raising thetemperature of a reproducing area to a temperature that allows thesaturated magnetization of the perpendicular magnetic recording layer toreach the vicinity of a maximum value.
 16. The magneticrecording-reproduction method according to claim 15, characterized inthat in the recording and reproducing processes, information is recordedand reproduced respectively while a recording area and a reproducingarea, which are placed in a direction perpendicular to the informationtrack direction, are allowed to have a temperature rise.
 17. Themagnetic recording-reproduction method according to claim 15,characterized in that in the recording and reproducing processes,information is recorded and reproduced respectively while a recordingarea and a reproducing area on the information track, which are placedin a direction with a predetermined angle with respect to theinformation track direction, are allowed to have a temperature rise. 18.The magnetic recording-reproduction method according to claim 15,characterized in that in the recording and reproducing processes, therecording area and the reproducing area are respectively subjected to atemperature rise by applying a light beam thereon.
 19. The magneticrecording-reproduction method according to claim 18, characterized inthat in the recording and reproducing processes, the recording area orthe reproducing area is subjected to a temperature rise by forming thelight beam into an elliptical shape and converging the resulting lightbeam thereon.
 20. The magnetic recording-reproduction method accordingto claim 18, characterized in that the recording area and thereproducing area are subjected to temperature rises by applying a lightbeam from the side where the recording-reproducing magnetic head isinstalled.
 21. The magnetic recording-reproduction method according toclaim 15, characterized in that in the recording and reproducingprocesses, the recording area or the reproducing area is subjected to atemperature rise by applying heat from a minute heat source system madeof a minute heat generating body.
 22. The magneticrecording-reproduction apparatus according to claim 3, characterized inthat each of the single magnetic pole heads is installed in a directionwith an angle not more than 45 degrees with respect to the informationtrack direction.
 23. A magnetic recording-reproduction apparatus, whichcarries out recording and reproducing processes on and from anmagnetic-reproducing medium on which a perpendicular magnetic recordinglayer made of a ferrimagnetic magnetic material whose magneticcompensation temperature is set to approximately room temperature isformed, characterized by comprising: a recording-reproducing magnetichead constituted by a plurality of single magnetic pole magnetic headshaving respective main magnetic poles whose length directions arealigned in the same direction as the information track direction of themagnetic recording-reproducing medium, the recording-reproducingmagnetic head carrying out both recording and reproducing on and fromrespective different tracks; and temperature-raising means for allowingone portion of an area facing the main magnetic poles of the respectivesingle magnetic pole heads in the perpendicular magnetization layer tohave a temperature rise.